It used to be common practice to knock on the neighbors door. Plus a lot of the residents were in their 30's like me.
I had some neighbors who moved in who smoked so I went outside on my porch to tell them it was okay with me to smoke outside although management wanted 30 ft away from the buildings.
So I told them I don't care if you smoke on the porch.
They got away with it for a while but someone bitched. I got the same notice for smoking cigars. I can't think of who narc'd them out, as their next door neighbors smoke tons of pot (and they got the same notice to smoke pot 30 ft away) but like I told the neighbors after they got a new sound system, don't play it after 2200 hrs, and I will knock on your door if it bugs me.
Someone ratted them out. They never smoke outside any more (good for the body) but they never smoke on the patio any more. I keep smoking a cigar ever few months. I told them not to worry about the letters. Smoking outside is not gonna kill anyone. Including my own kid. If I felt different I would let them know or never smoke a cigar again. Also, if I thought it a threat to my son's health I would knock on their door.
In any case the best thing to do is knock on the neighbors door and be civil. Be nice.